Re: 'Yes, you have to have one or the other. The usage note says:
"Either formatDesignation or formatRegistry should be recorded. Both are
optional, but since format (the container) is mandatory, one of these
must be used." '

I should have seen this for myself, but thank you Priscilla and Rebecca
for clarifying it for me.

Re Zhiwu Xie's comment: "Just to clarify, this is one or the other, not
one and/or the other, meaning I can't have both. Am I right?"

Would there be any reason to not allow both? If the formatRegistryKey
contained the format name (and version) it would be OK not to have
formatName as well, but if the formatRegistryKey was just a record
number, it would be nice to 'see' the format name without having to go
to the registry. If you allowed both, I suppose there could be ambiguity
if the formatName didn't match what was in the registry entry - however
even if you didn't allow both, ambiguity could occur, since
formatRegistry is repeatable and the occurrences could potentially
indicate different formats.

Bronwyn Lee
Australian Partnership for Sustainable Repositories
National Library of Australia
Canberra ACT 2600 Australia